Several treatments for disease require the removal of blood from a patient, processing the one or more components of the blood, and return of the processed components for a therapeutic effect. Those extracorporeal treatments require systems for safely removing blood from the patient, separating it into components, and returning the blood or blood components to the patient. With the advance of medical sciences, it has become possible to treat a patient's blood in closed-loop processes, returning the patient's own treated blood back to him in one medical treatment. An example of such processes include external treatment methods for diseases in which there is a pathological increase of lymphocytes, such as cutaneous T-cell lymphoma or other diseases affecting white blood cells. In such methods, the patient's blood is irradiated with ultraviolet light in the presence of a chemical or an antibody. Ultraviolet light affects the bonding between the lymphocytes and the chemical or antibody that inhibits the metabolic processes of the lymphocytes.
Photopheresis systems and methods have been proposed and used which involve separation of buffy coat from the blood, addition of a photoactivatable drug, and UV irradiation of the buffy coat before re-infusion to the patient. Extracorporeal photopheresis may be utilized to treat numerous diseases including Graft-versus-Host disease, Rheumatoid Arthritis, Progressive Systematic Sclerosis, Juvenile Onset Diabetes, Inflammatory Bowel Disease and other diseases that are thought to be T-cell or white blood cell mediated, including cancer. Apheresis systems and methods have also been proposed and used which involve separation of blood into various components.
During one of these medical treatments, a centrifuge bowl, such as, for example, a Latham bowl, as shown in U.S. Pat. No. 4,303,193, expressly incorporated by reference in its entirety herein, is operated to separate whole blood into red blood cells (“RBCs”), plasma, and huffy coat. The Latham bowl is a blood component separator that has been used for some time in the medical apheresis market as well as in innovative medical therapies such as extracorporeal photopheresis (ECP). PCT Applications WO 97/36581 and WO 97/36634, and U.S. Pat. Nos. 4,321,919; 4,398,906; 4,428,744; and 4,464,166 provide descriptions of extracorporeal photopheresis, and are hereby expressly incorporated by reference in their entirety.
Latham bowl efficiency is often measured by the white blood cell (“WBC”) “yield,” which is typically about 50%. Yield is defined as the percentage of cells collected versus the number processed. When compared to other types of whole blood separators, this high yield enables the Latham bowl separator to collect much larger volumes of WBCs while processing much less whole blood from the donor patient. However, a major drawback to the Latham bowl separator is that the separation process must be repeatedly stopped to remove the packed RBCs and plasma once they fill the inside of the bowl, creating a “batch-type” treatment process. Although the Latham bowl separator has a high volume yield, the constant filling and emptying of this bowl wastes time; thus, the process is considered less efficient with respect to time.
Prior photopheresis and apheresis systems and methods usually require batch processes and therefore take several hours to treat a patient or to obtain a sufficient supply of separated blood fragments. Furthermore, the systems are very complex to manufacture. It is a constant objective to reduce the time it takes to perform a complete photopheresis treatment session. Another objective is to reduce the amount of blood that must be drawn form a patient and processed in closed-loop processes per photopheresis treatment session. Yet another objective to increase the amount of white blood cell yield or obtain a cleaner cut of buffy coat per volume of whole blood processed.